Field of the Invention
The present invention relates to an electrical circuit having an SG full bridge circuit, to a load cell, to a load detection device, for example for a working platform, and to a vehicle comprising a load detection device. In particular, the present invention relates to a drift indicator for monitoring the equilibrium within the Wheatstone SG full bridge.
Discussion of the Known Art
Full bridge circuits comprising SG (strain gauge) elements may be used to determine load states at mechanically deformable elements. An example of this is a load or weigh cell which is arranged between a working platform and a crane, wherein a deformation of elements of the load cell allows drawing conclusions as to a loading by the working platform on the crane.
In a correctly operating load cell comprising an SG full bridge, there is an equilibrium as regards the electrical voltages occurring. A zero drift destroys this equilibrium so that a load state measureable by the electrical voltages deviates from an actual load state. This may result in the crane to be overloaded, since an overload is indicated too late.
In order to avoid such miss-indications, redundant SG full bridges are used in order to recognize zero drift of a SG full bridge by another one. However, this is of disadvantage in that, with deviating results of the two redundant SG full bridge circuits, only a deviating result is obtained which, however, may also be attributed to different material expansion at different locations of the different SG full bridges. In addition, several full bridge circuits have to be arranged and evaluated.
Some known concepts provide for monitoring the output signal of the full bridge circuit in an unloaded state. A deviation of the signal value from a zero value can be recognized to be the zero drift. However, this is not possible during operation since the operation itself produces a signal value which is different from the zero value.
Consequently, a concept would be desirable which allows reliably recognizing or ensuring operability of an SG full bridge.